Urza, Lord High Artificer

When Urza, Lord High Artificer enters, create a 0/0 colorless Construct artifact creature token with "This creature gets +1/+1 for each artifact you control."
Tap an untapped artifact you control: Add {U}.
{5}: Shuffle your library, then exile the top card. Until end of turn, you may play that card without paying its mana cost.

Contraption Cannon

{2}, Sacrifice Contraption Cannon: It deals damage to any target equal to the number of Contraptions you control.

Garbage Elemental

When Garbage Elemental enters, it assembles a Contraption. (Put the top card of your Contraption deck face up onto one of your sprockets.)
Undying (When this creature dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)

Tezzeret, Master of the Bridge

Creature and planeswalker spells you cast have affinity for artifacts. (They cost {1} less to cast for each artifact you control.)
+2: Tezzeret, Master of the Bridge deals X damage to each opponent, where X is the number of artifacts you control. You gain X life.
−3: Return target artifact card from your graveyard to your hand.
−8: Exile the top ten cards of your library. Put all artifact cards from among them onto the battlefield.

Urza, Academy Headmaster

+1: Head to AskUrza.com and click +1.
−1: Head to AskUrza.com and click -1.
−6: Head to AskUrza.com and click -6.

Steamfloggery

Roll a six-sided die. Assemble a number of Contraptions equal to the result. (To assemble a Contraption, put the top card of your Contraption deck face up onto one of your sprockets.)

Riveting Rigger

When Riveting Rigger enters, you may sacrifice another artifact. If you do, put two +1/+1 counters on Riveting Rigger and it assembles a Contraption. (Put the top card of your Contraption deck face up onto one of your sprockets.)

Meria, Scholar of Antiquity

Tap an untapped nontoken artifact you control: Add {G}.
Tap two untapped nontoken artifacts you control: Exile the top card of your library. You may play it this turn.

Overt Operative

Menace
Whenever Overt Operative deals combat damage to a player, it assembles a Contraption. (Put the top card of your Contraption deck face up onto one of your sprockets.)

Joyride Rigger

When Joyride Rigger enters, it assembles a Contraption. (Put the top card of your Contraption deck face up onto one of your sprockets.)

Chipper Chopper

Flying
When Chipper Chopper enters, you may sacrifice another artifact. If you do, put two +1/+1 counters on Chipper Chopper and it assembles a Contraption. (Put the top card of your Contraption deck face up onto one of your sprockets.)

Kindly Cognician

Spells you cast that refer to artifacts or Contraptions in their rules text cost {1} less to cast.

Shimmer Dragon

Flying
As long as you control four or more artifacts, Shimmer Dragon has hexproof. (It can't be the target of spells or abilities your opponents control.)
Tap two untapped artifacts you control: Draw a card.

Steamflogger Service Rep

Whenever another Goblin you control enters, you may pay {1}. If you do, Steamflogger Service Rep assembles a Contraption. (Put the top card of your Contraption deck face up onto one of your sprockets.)

Clock of DOOOOOOOOOOOOM!

{4}, {T}: Move the CRANK! counter to your Contraption deck's next sprocket and crank any number of that sprocket's Contraptions.

Steamflogger Temp

{6}, {T}: Steamflogger Temp assembles a Contraption. (Put the top card of your Contraption deck face up onto one of your sprockets.)

Steamflogger of the Month

When Steamflogger of the Month enters, it assembles a Contraption for each Contraption you control. (To assemble a Contraption, put the top card of your Contraption deck face up onto one of your sprockets.)

Aerial Toastmaster

Flying
{3}{W}, Sacrifice another artifact: Aerial Toastmaster assembles a Contraption. (Put the top card of your Contraption deck face up onto one of your sprockets.)

Spell Suck

Counter target spell, then assemble a Contraption. (Put the top card of your Contraption deck face up onto one of your sprockets.)

Midlife Upgrade

As an additional cost to cast this spell, sacrifice X Contraptions.
Assemble X plus one Contraptions. (To assemble a Contraption, put the top card of your Contraption deck face up onto one of your sprockets.)

Steamflogger Boss

Other Riggers you control get +1/+0 and have haste.
If a Rigger you control would assemble a Contraption, it assembles two Contraptions instead.

Incite Insight

Assemble X Contraptions. (To assemble a Contraption, put the top card of your Contraption deck face up onto one of your sprockets.)

Work a Double

Assemble two Contraptions. (Put the top card of your Contraption deck face up onto one of your sprockets. Then repeat this process.)

Wrench-Rigger

When Wrench-Rigger enters, it assembles a Contraption. (Put the top card of your Contraption deck face up onto one of your sprockets.)

Very Cryptic Command

Choose two —
• Switch target creature's power and toughness until end of turn.
• Target creature can't be blocked this turn.
• Draw a card. If that card's art is by Wayne England, you may reveal it and draw another card.
• Assemble a Contraption.

First Pick

Destroy target artifact or enchantment. Assemble a Contraption. (Put the top card of your Contraption deck face up onto one of your sprockets.)

Steady-Handed Mook

Deathtouch
When Steady-Handed Mook enters, it assembles a Contraption. (Put the top card of your Contraption deck face up onto one of your sprockets.)

Saheeli, the Gifted

+1: Create a 1/1 colorless Servo artifact creature token.
+1: The next spell you cast this turn costs {1} less to cast for each artifact you control as you cast it.
−7: For each artifact you control, create a token that's a copy of it. Those tokens gain haste. Exile those tokens at the beginning of the next end step.
Saheeli, the Gifted can be your commander.